The present invention relates to arc flash prevention and mitigation technologies, and particularly relates to prevention of nuisance tripping in low voltage circuit breakers.
Electric power circuits and switchgear have conductors separated by insulation. Air space often serves as part or all of this insulation in some areas. If the conductors are too close to each other or voltage exceeds the insulation properties, an arc can occur between conductors. Air or any insulation (gas or solid dielectrics) between conductors can become ionized, making it conductive, which enables arcing. Arc temperature can reach as high as 20,000° C., vaporizing conductors and adjacent materials, and releasing significant energy.
Arc flash is the result of a rapid energy release due to an arcing flash between phase-phase, phase-neutral, or phase-ground. An arc flash can produce high heat, intense light, pressure waves, and sound/shock waves. However, the arc flash current is usually much less than a short circuit current, and hence delayed or no tripping of circuit breakers is expected unless the breakers are selected to handle an arc flash condition. Agencies and standards such as the National Environmental Policy Act (NEPA), Occupational Safety and Health Administration (OSHA), and Institute of Electrical and Electronics Engineers (IEEE) regulate arc flash issues through personal protective clothing and equipment, but there is no device established by regulation to eliminate arc flash.
Typically, an arc flash is detected, at least in part through the use of a light-sensor or a photo-detector that detects light emitted by the arc. These light sensors are very sensitive to light and may be triggered by a bright light from the surrounding environment. This sensitivity to ambient light conditions results in nuisance tripping of the circuit breaker causing unnecessary loss of electrical power to the protected circuit.
Accordingly, while present arc flash detection systems are suitable for their intended purposes, there is a need in the art for an arc flash detection arrangement that reduces or eliminates the false detection of arc flash events.